German Offenlegungsschrift No. 2,526,788 published Dec. 23, 1976 discloses that the oxidation of certain 17-alkanoyloxy-.DELTA..sup.16 -steroids with osmium tetroxide opens the D-ring of the steroids yielding a 16,17-seco-steroid of the type ##STR2## wherein "St" symbolizes A, B and C rings of the steroid and R symbolizes methyl or ethyl. Ring closure of the 16,17-seco-steroid pictured above yields a D-homo-oxasteroid of the type ##STR3## Subsequent treatment of the 17-oxa-17a-oxo-D-homo-steroid yields a steroid of the type ##STR4##
Ozonolysis of certain 17-acetoxy-.DELTA..sup.16 -estrenes followed by ring closure (using p-toluenesulfonic acid) of the resulting seco-steroids, is taught by Baran in U.S. Pat. No. 3,257,412 to yield 17-oxo-D-homoestrenes.
Iriarte et al., J. C. S. Chem. Comm., 1110 (1972), describe the osmium tetroxide oxidation and subsequent periodic oxidation of the enol acetate having the structure ##STR5## to yield a compound having the structure ##STR6##
Kuo et al., J. Org. Chem., 28, 1619 (1963), describe the preparation of a 17-oxa-D-homopregnane having the structure ##STR7##